improve libevent2 handling

* add configure check
* change the way the headers are required (copied from tmux)

configure

@@ -242,6 +242,7 @@ runtest getprogname	GETPROGNAME	|| true
 runtest imsg		IMSG		-lutil || true
 runtest landlock	LANDLOCK	|| true
 runtest libevent	LIBEVENT	|| true
+runtest libevent2	LIBEVENT2	|| true
 runtest libtls		LIBTLS		|| true
 runtest openssl		OPENSSL		|| true
 runtest pr_set_name	PR_SET_NAME	|| true
@@ -320,6 +321,7 @@ cat <<__HEREDOC__
 #define HAVE_IMSG		${HAVE_IMSG}
 #define HAVE_LANDLOCK		${HAVE_LANDLOCK}
 #define HAVE_LIBEVENT		${HAVE_LIBEVENT}
+#define HAVE_LIBEVENT2		${HAVE_LIBEVENT2}
 #define HAVE_PROGRAM_INVOCATION_SHORT_NAME ${HAVE_PROGRAM_INVOCATION_SHORT_NAME}
 #define HAVE_PR_SET_NAME	${HAVE_PR_SET_NAME}
 #define HAVE_QUEUE_H		${HAVE_QUEUE_H}

gmid.h

@@ -26,7 +26,6 @@
 #include <netinet/in.h>
 
 #include <dirent.h>
-#include <event.h>
 #include <limits.h>
 #include <netdb.h>
 #include <signal.h>
@@ -38,6 +37,19 @@
 
 #include <openssl/x509.h>
 
+#if HAVE_EVENT2
+# include <event2/event.h>
+# include <event2/event_compat.h>
+# include <event2/event_struct.h>
+# include <event2/buffer.h>
+# include <event2/buffer_compat.h>
+# include <event2/bufferevent.h>
+# include <event2/bufferevent_struct.h>
+# include <event2/bufferevent_compat.h>
+#else
+# include <event.h>
+#endif
+
 #define GMID_STRING	"gmid " VERSION
 #define GMID_VERSION	"gmid/" VERSION
 

have/libevent2.c

@@ -0,0 +1,56 @@
+/*
+ * Copyright (c) 2021 Omar Polo <op@omarpolo.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <sys/time.h>
+
+#include <event2/event.h>
+#include <event2/event_compat.h>
+#include <event2/event_struct.h>
+#include <event2/buffer.h>
+#include <event2/buffer_compat.h>
+#include <event2/bufferevent.h>
+#include <event2/bufferevent_struct.h>
+#include <event2/bufferevent_compat.h>
+
+static void
+rw_cb(struct bufferevent *bev, void *d)
+{
+	return;
+}
+
+static void
+err_cb(struct bufferevent *bev, short err, void *d)
+{
+	return;
+}
+
+int
+main(void)
+{
+	struct bufferevent *bev;
+
+	event_init();
+
+	if ((bev = bufferevent_new(0, rw_cb, rw_cb, err_cb, NULL)) == NULL)
+		return 1;
+
+	evbuffer_unfreeze(bev->input, 0);
+	evbuffer_unfreeze(bev->output, 1);
+
+	bufferevent_free(bev);
+
+	return 0;
+}